1. Field of the Invention
The invention relates to an alloy, in particular for an anti-friction coating, comprising elements which form a matrix and at least a soft phase and/or a hard phase, which soft phase elements and/or hard phase elements produce a solid solution or bond with the matrix element, an anti-friction coating, in particular a bearing anti-friction coating made from the alloy, a composite material comprising at least a first peripheral coating and a second peripheral coating disposed opposite it, for example a protective coating of steel, in particular for anti-friction bearings or thrust washers, a method of producing the composite material and the use of the alloy to produce an anti-friction coating for an anti-friction bearing or a thrust washer or for directly coating components subjected to friction stress.
2. Description of the Related Art
Technical progress made in the engine construction industry has meant that increasingly tough requirements are being placed on many aspects of anti-friction elements, such as plain bearings or thrust washers or sliding bushes for example. The anti-friction element or its anti-friction coating should be soft enough to enable it to adapt well to faults of the co-operating anti-friction element caused by production on the one hand, but the anti-friction coating should be sufficiently hard or have a high enough strength to exhibit good durability or bearing capacity during operation at high speeds and when subjected to vibrations or high mechanical stress, on the other hand. The properties which can be achieved in these anti-friction coatings and bearings always mean having to strike a compromise. If the emphasis is on good running-in or resistance to galling, the anti-friction coating itself is usually only able to withstand low mechanical stress because the forces to which the shaft or the bearing is exposed are transmitted as a whole and exclusively by the soft anti-friction coating which is therefore susceptible to wear at an early stage. If, on the other hand, elements are provided which are capable of withstanding such abrasion, they are so at the expense of reduced ability of the coating to adapt.
In the case of standard coatings made by hot metal processing techniques, such as disclosed in patent specifications WO 97/22725 A or DE 39 06 402 C2, an attempt is made to combine these intrinsically contradictory property profiles by alloying an element which forms the matrix of the material, elements which form the soft phases, such as lead, tin, zinc or bismuth, for example, so that the coating is able to adapt and embed pieces abraded from the parts to be supported, e.g. shafts. In order to increase the strength and bearing capacity, other elements are incorporated in the alloy which form a hard phase, for example inter-metallic compounds or mixed crystals. Depending on the content of the different elements, the emphasis will therefore be on good ability to embed or good resistance to galling or high bearing capacity.
Also quite common are anti-friction elements made from copper-based materials, for example, which as a rule have a high grinding resistance due to elements forming soft phases, such as lead. Due to the fact that it does not mix or as a result of the gaps which occur when copper and lead are mixed, the lead separates and disperses in the copper matrix and is responsible for the good tribological properties of this material.
Thermally sprayed coatings for runner blades are known from patent specification DE 198 09 721 A1, and the coating has a higher degree of hardness than the underlying metal base in order to increase resistance to abrasion. Amongst the coating materials mentioned are alloys with a base of Ni, Co, Fe, cermets or hard metals.
Patent specification EP 0 911 425 A1 describes a method of spraying cold gas as a means of coating substrate materials. Amongst others, nitrogen, argon, neon, xenon or carbon dioxide are mentioned as a process gas. Overall, the intention is to improve the quality of the coating on the basis of an appropriate temperature, pressure and particle velocity.